This is the second consecutive year that M&S has been ranked No. 1 for the depth of its carbon measurement and reporting practices. Aviva and Unilever round out top five FTSE 100 companies with the highest carbon performance.

All companies in Carbon Clear’s 2013 report were scored in four subject areas: measurement, reporting and verification; carbon strategy; carbon reduction; and engagement. Carbon Clear conducted its research in July 2013 using publicly available data. Documents reviewed included corporate sustainability reports, annual reports and additional links from company websites, including sustainability microsites.

Each company was mapped to Carbon Clear’s so-called carbon maturity curve — a five-stage process charting the evolution from basic carbon management activities to a developed, integrated strategy.

Companies scored best in the management reporting and verification performance area with an average score of 63 percent. Last year, companies had an average score of 58 percent.

Carbon Clear’s report says a small number of companies were leaders in reporting supply chain Scope 3 emissions (see graphic). Some 26 companies are reporting Scope 3 emissions beyond business, the report says. Four companies — BT Group, M&S, Unilever and British Land Company — excelled at providing proof of reductions with another 21 providing limited evidence.

Carbon Clear’s research found just over half of FTSE 100 companies disclose their carbon footprint in their annual report. Other key findings include 29 companies have carbon targets to or beyond 2020 and 41 percent of companies showed evidence they are willing to go beyond just reporting their emissions and are looking at risk mitigation and adaptation strategies associated with climate change.

Some 69 percent of companies set some kind of carbon reduction target and 17 companies are exceeding their stated targets, the report says.